1. Field of the Invention
The present invention relates to restoration of a lake having a high saline content. More particularly, the present invention relates to an improved method of restoring a highly saline lake that utilizes inner and outer dikes or levees (preferably concentrically positioned), elongated smaller lakes formed between the dikes, a central area providing one or more breathing brine fields, wherein salinity of inflow gradually increases from outer lake to the inner lakes to the breathing brine field or fields. In the process, the overall lake water inflow needed to maintain several separate yet healthy lake ecosystems can be reduced.
2. General Background of the Invention
The Salton Sea is located in a closed basin in Riverside and Imperial Counties in southern California, south of Indio and north of El Centro. The Salton Sea is more than 220 feet below sea level and has no natural outlet. The Salton Sea Basin is part of the lower Colorado River delta system. Historically, lakes have existed in this basin as the course of the Colorado River has shifted. The current body of water (Salton Sea) was formed in 1905 when a levee break along the Colorado River caused flows from the Colorado River to enter the basin for about 18 months. Since 1905, the Salton Sea has fluctuated in size with varying inflow. It recently has had a surface area of 365 square miles.
Currently, the Salton Sea is filled by the agricultural runoff from the Colorado River Basin. In particular, approximately 80% of Salton Sea inflows come from the Imperial Valley. Since the Salton Sea has no outlet, evaporation produces the only export of water. Nearly all constituents in the inflow, such as salts, nutrients and fertilizers remain in the Salton Sea. Currently, the Sea is approximately 25% saltier than ocean water, with a continuing trend of increasing salinity. Eventually, a point will be reached where current biological activity in the Sea will cease, as is the case with other highly saline lakes such as Mono Lake. Under these highly saline conditions the benthic organisms that support the current ecology of the Salton Sea could no longer survive. The fisheries supported by those organisms would likewise disappear, and have practically vanished already. An ecology based on organisms adapted to highly saline conditions, such as brine shrimp, would result. Even under existing conditions, a project for the restoration of the Salton Sea (including improvement and stabilization of the water quality) is critically needed.
Accelerating these effects would be the reduced inflows to the Salton Sea anticipated under the 2003 Quantification Settlement Agreement (QSA). The QSA provides for the phased transfer of up to 560,000 acre-feet per year of water from agricultural to urban uses, resulting in a significant reduction of agricultural flows to the Sea, of at least 300,000 acre-feet per year. It is assumed that a water transfer of approximately the scale of that contemplated by the QSA will result in reduced inflows to the Salton Sea.
In future years, additional transfers may also occur as demand increases in the expanding urbanized areas of Southern California. For example, the Metropolitan Water District of Southern California (MWD) has pending a water rights application with the State Water Resources Control Board (SWRCB) seeking to divert all of the flows from the Alamo River and other agricultural sources that would otherwise reach the Salton Sea.
Filed in 1997, MWD's application contends that it has the right to take much of the inflow of the Salton Sea and divert it to its service area for various uses. MWD supplemented its application in June 2004 and reiterated that it continues to seek the inflows for diversion, although it recognizes that the amount of the inflows may be reduced due to various conservation measures described in the QSA.
If an appropriate Salton Sea restoration plan is not implemented, a substantial portion of the inflow may be diverted permanently from the Salton Sea area such that no restoration would be possible. The resulting reduction in inflows would be severe, ranging from approximately 400,000 to 450,000 acre feet per year, with net inflows to the Salton Sea being reduced to as low as 468,000 acre feet per year (assuming diversions comparable to that contemplated under the QSA).
Over time, those smaller inflows will result in a reduction in the surface area of the Sea. This reduction could expose previously inundated sediments. The reduced water volume in the Salton Sea will also result in a corresponding increase in salinity. Without affirmative restoration activities, a number of adverse environmental consequences would result, such as a reduction of the Sea's important habitat values for the Pacific Flyway, increased air pollution, and decreased aesthetics values.
Any restoration plan must solve both of the key problems faced by the Salton Sea, water quality and water quantity. Over the years, a number of options have been explored for addressing these concerns. In 1998, the Salton Sea Authority, in a joint lead with the federal Bureau of Reclamation, initiated an environmental review of a number of alternatives to address the problems that existed at the time. These alternatives primarily focused on “whole-sea” restoration approaches such as the conveyance of water to and/or from the ocean to address the elevation and salinity problems, various evaporation options to facilitate the removal of salt, and desalination options using vertical tube evaporation technology. This effort, however, was not completed, primarily due to critical problems identified with all of the alternatives being evaluated, such as excessive costs or environmental impacts.
In April 2004, the Salton Sea Authority (SSA) evaluated four “reasonable” restoration alternatives: (1) no marine lake; (2) south marine lake without elevation control; (3) south marine lake with elevation control, and (4) north marine lake with elevation control. The SSA ultimately concluded that the North Lake concept, combined with other features, was its preferred project.
After much discussion between DWR and the interested parties, four alternatives, two of which draw upon the work completed by the Salton Sea Authority in 2004, gained prominence as a reasonable range for the alternatives evaluation: (1) the “Low Sea” alternative, which allows the sea level to drop and involves the construction of a relatively small brine pond, (2) the “Shore Lake” alternative, which involves the creation of a relatively deep short lake along the entire perimeter of the current sea, separated from a dry area and brine pond in the interior by a dike (similar to the SSA's In-Sea Solar Evaporation Pond alternative, but with a different configuration), (3) the “North Lake” alternative (the SSA's “North Lake with elevation control” alternative) which separates the sea with a relatively high dam and allows the southern portion of the lake to largely dry out, except for a brine pond, and (4) the “South Lake” alternative (the SSA's “South Lake with elevation control” alternative) which is similar to the North Lake alternative with the dry areas and brine pond to the north.
The Salton Sea Reclamation Act of 1998 formulates the goals of the restoration as follows: continue to use the Sea as a reservoir for irrigation drainage; reduce and stabilize the overall salinity of the Sea; stabilize surface elevation of the Sea; reclaim, in the long-term, healthy fish and wildlife resources and their habitats; and enhance the potential for recreational uses and economic development of the Sea.
The 2000 Draft EIS/EIR on restoration of the Salton Sea prepared by USER and the Salton Sea Authority revised the fourth of these objectives as follows: provide a safe, productive environment at the Sea for resident and migratory birds and endangered species.
The state QSA implementing legislation requires that the preferred alternative provide, to the maximum extent feasible, for attainment of three key objectives, which further refine the habitat objective and add an objective relating to the air quality impacts: restoration of long-term stable aquatic and shoreline habitat for the historic levels and diversity of fish and wildlife that depend on the Salton Sea; elimination of air quality impacts from the restoration projects; and protection of water quality.
Additionally, in order to be successful, the project will need to be economically viable, implying the following objective: plan, construct, develop and operate the restoration project within the practical economic constraints of available funding sources and maximizing economic benefits.
As with these economic factors, in order to be successful the project must be one that can receive all required permits and other entitlements, satisfying the following objectives: qualify the project as the Least Environmentally Damaging Alternative under the Clean Water Act 404(b) (1) guidelines; ensure that the project avoids jeopardy to endangered or threatened species, or the adverse modification of designated critical habitat, and otherwise meets USFWS permitting requirements; comply with Clean Air Act general conformity requirements; and fully comply with all other regulatory programs.
A number of other practical factors also need to be addressed in the selection and implementation of an alternative: 1) ensure timely achievement of project benefits; 2) maximize collateral benefits of the project, particularly the provision of effective water storage capacity that can assist in the management of fluctuating Colorado River flows, and conveyance of water from the IID inflows to other potential users; 3) allow for flexibility of design and construction, in particular to adjust to the actual pattern of water transfers over the coming decades; 5) minimize seismic risks; 6) maximize public acceptance; and 7) maximize the active participation of the local residents in the construction of the project.
The following U.S. Patents are possibly related to lake restoration and are each incorporated herein by reference.
TABLEPAT. NO.TITLEISSUE DATE5,807,030Stabilizing Elements forSep. 15, 1998Mechanically StabilizedEarthen Structure5,902,070Geotextile Container andMay 11, 1999Method of Producing Same6,623,214Modification of GeotextileSep. 23, 2003Tubes6,626,611Beach Restoration andSep. 30, 2003Regeneration Systems, Methodsand Compositions6,726,406In Situ Formation of ReactiveApr. 27, 2004Barriers for Pollution Control6,773,595Compartmentalized FacultativeAug. 10, 2004Lagoon and Method of Creatingand Maintaining Such a Lagoon